Not quite sure how you got this from what you quoted, but ultimately that is a possibility. If one player attacks another and the defender has an Alliance with a nearby friend, the Alliance system may invite that friend to help his ally. I'm sure, however, that such a system would be governed by the rules of balance. For example, if a level 5 player (let's say) accepted a challenge from a level 10 player, the game may search a list of his Allies for another level 4-6 player who could come to his aid. This could even out the engagement and provide an extra layer of complexity to the fight for the higher level to deal with. Now, if your concern is whether or not two or three high-level players could come along and wage war on your little town? No, that can't happen because all PvP is consensual--you would have to agree to fighting them, and assuming the skill parity is far enough apart, it would cost you nothing in tribute to say "No, thanks".

Generally speaking, that would be true, but the devs had said elsewhere (I'll go dig it up if you'd like, I think it's in the suggestions forum) that there is a distinct possibility of uneven matchups so long as the field of battle is ultimately deemed equal. That is, if three level 4 players were fighting one level 14 player, the matchmaking system may see that as roughly equivalent and allow it to commence. After all, it can be a massive advantage to have three brains with smaller forces to manage against a single brain managing many units.

Keep in mind that my use of "levels" here is totally arbitrary and for example purposes only; I have no idea what the actual progression system in DoF looks like at this point.

If there are level restrictions then it doesn't make sense to allow people so far down in the leveling scheme to attack someone 10 or more level higher....It might be like within a reasonable limit like 4 level 4 players attacking 1 level 8 player